A device of particular interest for high power and/or high frequency applications is the High Hole Mobility Transistor (HHMT), which is also known as a modulation doped field effect transistor (MODFET). These devices may offer operational advantages under a number of circumstances because a two-dimensional hole gas (2DHG) is formed at the heterointerface of two semiconductor materials with different bandgap energies, and where the smaller bandgap material has a higher electron affinity. The 2DHG is an accumulation layer in the undoped (“unintentionally doped”), smaller bandgap material and can contain a very high sheet hole concentration in excess of, for example, 1013 carriers/cm2. Additionally, holes that originate in the wider-bandgap semiconductor transfer to the 2DHG, allowing a high hole mobility due to reduced ionized impurity scattering.